CHAPTER 5 AEROBATICS AND FORMATION FLYING 1. There is much more to flying than just taking off and landing. RAF training involves a sequence of carefully graded air exercises, which are far beyond the scope of this manual. However, to give you a flavour of what is involved, in this chapter we shall cover the rudiments of two of the more advanced aspects of military flying aerobatics and formation flying. Also, you will find it useful to have some knowledge of these skills when you see them performed at air displays. AEROBATICS 2. Introduction. In the early days of air fighting aerobatics were used by pilots to manoeuvre into a favourable firing position, or to avoid the guns of enemy aircraft. Although today aerobatics are little used in aerial combat, they are of great importance in the training of Royal Air Force pilots. They give the pilot confidence in handling his machine in all possible attitudes and accustom him to the high strains he will experience when executing certain manoeuvres during combat fights. 3. Before starting any aerobatic exercise, the pilot must always carry out the following checks, which are remembered using the mnemonic HASELL. a. Height sufficient to perform the complete manoeuvre without descending below the prescribed minimum. b. Airframe check that flaps and undercarriage are UP, airbrakes tests and IN. c. Security all equipment and loose articles should be stowed and the seat harness locked and tight. d. Engine all temperatures and pressures normal and fuel sufficient for the exercise. e. Location make sure that the aerobatics will take place in air space clear of Active airfields, Built-up areas and Controlled airspace. To avoid the possibility of getting lost, select a suitable landmark and keep a position check on it. f. Look-Out keep well clear of all other aircraft and cloud, vertically and horizontally, throughout the exercise. BASIC MANOEUVRES 4. An aircraft can be manoeuvred in three planes (Fig 5-1). In aerobatics the looping and rolling planes are mainly used, sometimes separately and sometimes in combination. In only a few manoeuvres is the yawing plane used. The best way to understand aerobatics is to see what can be done with an aircraft in each plane in turn, and then to see what is possible when the manoeuvres in different planes are combined. 34.3.5-1
Fig 5-1: The Three Planes of Movement 5. The Loop. The most basic manoeuvre, and the one which is always the first to be taught to pilots during their training, is the loop. In this aerobatic the pilot uses a line feature such as a river or railway line on the ground as a visual reference on which to keep straight. If necessary, he places the aircraft in a shallow dive to gain speed, then taking care to keep the wings level, he raises the nose until the horizon disappears below his field of view. When this happens, he looks as far back over his head as he can and watches for the opposite horizon to come round. As soon as he sees it he checks that his wings are still level. At the top of the loop the airspeed is quite low, and if the loop is pulled too tight the aircraft may stall. So the pilot coaxes it over the top and down the other side, still keeping straight on his line feature. The speed builds up quite quickly on the way down, so that at the end of the aerobatic the pilot has enough airspeed to go into another manoeuvre (Fig 5-2). 6. The Barrel Roll. In the rolling plane, the simplest manoeuvre is the barrel roll, where the aircraft rolls around a point just above the horizon. To do this the aircraft is put into a shallow dive until the correct airspeed is reached then banked 45 in the opposite direction to that in which the roll is to be made. The pilot then flies the aircraft round the outside of an imaginary barrel. The diameter of the barrel may be small or large (but if it is very small it begins to look like the next aerobatic described, the slow roll). Fig 5-2 shows the barrel-shaped path of the aircraft, and a spot above the horizon (usually a small cloud) chosen by the pilot. The small diagram also shows how the cockpit coaming appears to move in a circle around the chosen cloud, as seen by the pilot. A line feature is always useful when practising a barrel roll the pilot will use it to check that the centreline of the barrel keeps track with the line feature. 34.3.5-2
Fig 5-2: Barrel Roll 34.3.5-3
7. The Slow Roll. The slow roll is a rather more difficult manoeuvre. The pilot rolls the aircraft keeping the nose on a point on the horizon instead of round a point just above it. He must coordinate his controls very carefully to do the aerobatic smoothly and well. In a good slow roll the aircraft will neither lose nor gain height (Fig 5-3). The rate of roll may vary from one manoeuvre to another, but for each roll, the rate of roll should be constant from beginning to end. A fast roll is easier to fly than a really slow one. Fig 5-3: Slow Roll 34.3.5-4
8. The Staff Turn. The stall turn is the only basic manoeuvre in the yawing plane. From level flight, or a shallow dive if extra speed is needed, the pilot eases back the stick to bring the nose up to the vertical position. He holds the aircraft there while the speed falls off. Just before the stall, he applies full rudder to yaw the aircraft round to one side. As the nose comes over, engine power is taken off and the aircraft falls sideways until it is pointed vertically down. The speed rapidly increases, and the pilot then raises the nose with the wings level and the aircraft points back in the direction from which it came; it has turned through 180 (Fig 5-4). Fig 5-4: Stall Turn 34.3.5-5
9. Roll off the Top. Properly called a half roll off the top of a loop, this manoeuvre consists of the first half of a loop followed by half of a slow or barrel roll. It looks better and is slightly more difficult to perform if a slow roll is chosen (Fig 5-5). Fig 5-5: Half Roll off the Top of a Loop 34.3.5-6
ADVANCED MANOEUVRES 10. All other aerobatics consist of variations or combinations of the basic manoeuvres described above. 11. Half Rolland Pull Through. This is the opposite of a half roll off the top of a loop. It consists of a first half of a slow roll followed by the second half of a loop (Fig 5-6). As the airspeed builds up very rapidly in the second half of the manoeuvre, when the aircraft is going downwards, the speed of entry to the first part (the half roll) must be kept low. Otherwise, in the half loop the maximum permissible speed or the maximum permitted g limit (or both) might be exceeded. It helps if the power is reduced on entering the half loop. This manoeuvre always involves a considerable loss of height. Fig 5-6: Half Roll and Pull Through 34.3.5-7
12. The Upward Roll. The rolling manoeuvres so far mentioned have all been about a horizontal axis. They can also be done about an inclined axis and in the extreme case about a vertical axis. The pilot needs plenty of speed to do an upward roll, so he dives, then raises the nose to the vertical position and rolls round the point directly above him. The roll is kept vertical position and rolls round a point directly above him. The roll is kept vertical by looking out at each wing tip in turn to see that they are both the same distance above the horizon. The airspeed falls off quickly in the upward roll and the pilot must not take too long in getting round. At the end of the roll he should have just enough airspeed to complete a stall turn. 13. Aileron Turn. The aileron turn is a roll flown vertically downwards (Fig 5-7). It may be started from a half roll or from, the second half of a loop; in either case it is started when the aircraft is pointing vertically down. In this manoeuvre speed increases very rapidly and a lot of height is lost. If necessary, power should be reduced and airbrakes opened to control the speed. Fig 5-7: Aileron Turn 34.3.5-8
14. The Derry Turn. If an aircraft is in a steep turn in one direction and the pilot wishes to go into a steep turn the other way, he usually rolls through the normal (upright) flying position. In the Derry turn, however, he rolls through the inverted position and may have to raise the nose slightly as he enters the manoeuvres to avoid losing any height (Fig 5-8). Fig 5-8: Horizontal Derry Turn (Plan View) 34.3.5-9
15. Vertical Eight. The vertical figure eight is a combination of a half roll off the top of a loop, a full loop, and a half roll and pull through (Fig 5-9). Speeds at entry and exit are high, and care is essential to avoid exceeding speed and g limits. Fig 5-9: Vertical Figure Eight 34.3.5-10
16. Horizontal Figure Eight. A horizontal figure eight is started as for a loop. The loop is held until the nose is below the horizon on its way down and the aircraft is then half-rolled and dived to gain sufficient speed to enter a further loop as shown in Fig 5-10. A variation on this manoeuvre is the Cuban eight, in which the aircraft is rolled on pulling up into the first loop, completing the loop and half rolling again when pulling up into the second loop. Fig 5-10: Horizontal Figure Eight 34.3.5-11
17. Hesitation Rolls. Hesitation rolls may be either four-point or eight-point rolls, the difference being that in the four-point roll the roll is temporarily halted after each 90 of roll and in the eightpoint roll after each 45 of roll. This manoeuvre can be flown more easily on some aircraft than others, but the higher the speed of entry the greater is the control available and the accuracy of the roll. 18. Inverted Flight. There are few aircraft in which it is permitted to perform prolonged inverted flight or inverted gliding. You are most likely to see some at air shows and when you do they will most probably be specially built or modified civilian aircraft. The main features of inverted flight are: a. Aircraft are not designed to take inverted g loads as much as they are for normal flight (for example, an aircraft might have a limit of + 6½g, but only 2g). Therefore, loading during inverted periods must be carefully controlled by the pilot. b. The aircraft responds normally when the controls are moved, but the movement of the aircraft relative to the horizon will be the reverse of that for the same control movements in normal flight. For example, to make a descending turn to the left (ie in a clockwise direction), the control column should be eased backwards and to the pilot s right to lower the nose and apply the required degree bank; right rudder should be applied to counteract slip. c. During inverted flight at a given speed, the lift coefficient is much lower resulting in an increased stalling speed. Because of the lower lift coefficient the wing must be set at a higher angle of attack than for the same speed in normal flight; see Fig 5-11. d. Due to lower wing efficiency and the high stalling speed, the gliding speed is higher when inverted; about one and a third times the normal gliding speed is generally suitable. e. The aircraft may be sensitive laterally because any dihedral now has a destabilizing effect. Fig 5-11: Inverted Flight 34.3.5-12
FORMATION FLYING INTRODUCTION 18. A formation is defined as an ordered arrangement of two or more aircraft proceeding together as an element. Their movement is controlled by an appointed leader termed No 1. The No 1 is responsible for briefing other members of the formation and for ensuring the safe conduct of the formation throughout the sortie. Detailed considerations of the No 1 s responsibilities and leadership are given at Paras 21 and 22 below. 19. There are two categories of formation flying: a. Close Formation used for: (1) Take offs, cloud penetration and landings used mainly by training and fighter aircraft. (2) Display and show purposes. b. Tactical Formation -= used for all tactical fighter operations. This type of formation is designed to provide all-round search, the best mutual crossover and the best mutual fire support. 20. Only close formation is discussed in this manual. Very briefly, pilots fly in close formation by ignoring their instruments and the horizon to which they normally refer, and concentrate on keeping a fixed position in relation to the leader. They do not take their eyes off him for a second. Aircraft in close formation have been a common sight at air displays for a number of years, and there has always been a very good use for such formations. A group of aircraft staying close together can be taken by their leader or directed by a controller on the ground to the target area. Three or four aircraft can be treated as one unit and thus be used together where they will do most good. They can also be brought back to base (or recovered to use the correct expression) as one unit. Instead of one controller trying to give Controlled Descent through Cloud to three or four separate aircraft, he gives instructions to the leader, and the others flying in close formation follow his movements. This mans that fewer controllers are needed and time is saved in recovering aircraft in bad weather. LEADERSHIP 21. Successful formation is heavily dependent on good leadership. The No 1 commands the formation and is immediately responsible for its security, the tactics and exercises to be flown and for its safe return to base. 22. The No 1 must fly in a position from which he can communicate with all of his pilots. He must be replaceable by a deputy leader who flies in a pre-arranged position relative to the No 1 and who must at any time be prepared to assume the responsibilities of the No 1. Thorough briefing before any formation flight is vital. Every member of the formation should know precisely the object of the exercise, the general plan of likely formation changes, the emergency procedures and action to be taken in the event of deterioration in weather and airfield state. Whenever possible, the service-wide standard positions and procedures should be used, and the principle of minimum change put into practice. Minimum Change means the smallest number of aircraft movements for any formation change. 34.3.5-13
THE SECTION 23. The basis of all formations is the section or element, which consists of two or more aircraft all operating under one nominated leader. Larger formations may be formed by the integration of two or more sections. Each section will have its own leader but a leader of the overall formation must also be nominated; he will normally be the No 1 of the lead section. SECTION FORMATIONS 24. The standard section formations are: a. Vic-three aircraft as shown in Fig 5-12. Fig 5-12: Vic Formation 34.3.5-14
b. Echelon with aircraft disposed as shown in Fig 5-13. Fig 5-13: Echelon 34.3.5-15
c. Line abreast with aircraft as shown at Fig 5-14 Fig 5-14: Line Abreast d. Line Astern with aircraft disposed as shown in Fig 5-15. Fig 5-15: Line Astern 34.3.5-16
e. Box with 4 aircraft as shown in Fig 5-16. (NB the only number of aircraft possible for Box is 4). Fig 5-16: Box 25. For cloud penetration the maximum size of a formation should normally be three. A three will invariably fly in Vic, and a pair as an Echelon, as it is essential for the formating pilots to see any hand signals made by the leader. CLOSE FORMATION FLYING TECHNIQUE 26. Relative Speeds The driver of a car subconsciously judges the speed of his vehicle in relation to others against a background of fixed objects trees, hoses, telegraph poles, etc which border the road. Such a background does not exist in the air and the only way in which a pilot can be sure of his speed is to look at the airspeed indicator (ASI). 34.3.5-17
27. Apparent Size. The difference in size of an aircraft viewed from six miles range and from three miles range is very small, but the difference in size of the same aircraft viewed from one mile and 800 yards is quite noticeable. The effect of this is that when one aircraft is overtaking another, even at a high closing speed, the rate of approach appears very low at long ranges (five to ten miles) and seems to increase almost imperceptibly until critical range is reached, when the overtaken aircraft appears to grow rapidly in size, and the true speed of approach can be judged. 28. Distance. Judgement of distance in the air is a matter of experience and practice but pilots can attain proficiency in the art more quickly if they realise that the tendency is to underestimate the rate of approach until the final stages. It is helpful, for the initial join-up if the No 1 flies at a constant, known airspeed; a pilot joining the formation can then set his own airspeed to give a reasonable but controllable overtake speed, eg 50 knots is a suitable speed advantage when the range to be closed is neither excessively long nor very short, but this will vary for different aircraft types. JOINING FORMATION 29. The time spent in joining formation serves no useful purpose and the longer the time taken to assemble a formation, the shorter will be the time that the formation can spend on the air exercise. Thus, pilots should join formation with the least possible delay. Fig 5-17: Joining Up After Take-Off 34.3.5-18
30. Fig 5-17 illustrates the procedure for joining formation after a stream take-off. The leading aircraft should take-off, and fly straight ahead for a distance varying from 800 yards to one mile, according to the type of aircraft, and thereafter commence a gentle turn. The second aircraft No 2 of the formation, should then turn inside the leading aircraft, so as to intercept it as soon as possible, and the third and fourth aircraft should carryout a similar procedure, ensuring that they always keep lower numbered aircraft visual while joining; the final join-up should normally be in numerical sequence. 31. It is important that the leading aircraft should settle down to the agreed cruising speed as soon as possible. The following aircraft may then fly with a small overtake speed (approximately 10-20 knots) gaining position by the use of shorter radius turns. In this manner leeway is rapidly made up and individual aircraft are able to take up their positions without excessive changes in airspeed. If the following aircraft either fly the same flight path as the leading aircraft or make a turn of larger radius outside the leaders flight path, they will have to increase their airspeed in order to overtake and will consequently be obliged to make a large alteration in airspeed before they can take their stations. Moreover, a great deal of time and fuel will be wasted. 32. It can be seen that once the joining aircraft is established in the shorter radius turn, all the pilot needs to do is maintain the interception course until he reaches the point at which he can decelerate and move to the correct formation position. To maintain the interception course the lead aircraft must remain in a constant position in the joining pilots field of view. If it moves forward the joining pilot must increase his rate of turn and if it moves backwards the rate of turn must be decreased. It must be remembered that, when the lead aircraft is stationary in the windscreen or canopy a collision course is set-up, so positive clearance in the vertical plane must be established in the later closing stages. POSITIONS IN BASIC FORMATION 33. The distance between aircraft in formation are laid down in relevant instructions and pilots must observe them strictly. No attempt should be made to practise formation flying in manoeuvres until the correct positions for each basic formation position has been learned. 34. When flying in vic or echelon a formation pilot will maintain station by reference to agreed features on the adjacent aircraft (eg, lining up the wing tip and the nose of the aircraft ahead). Obviously these features will vary according to aircraft type and can be varied on a specific type to achieve a particular formation shape for special occasions. 35. In line abreast formation, the correct fore and aft position can best be judged by reference to the cockpit of the next aircraft and the lateral position by reference to its size. The plane of the windscreen arch may assist fore and aft positioning but it is difficult to judge whether one aircraft is truly abreast with another and the tendency is to formate a little too far back. It will be difficult to judge the separation between the wing tips of aircraft with highly swept wings and extra caution will then be needed. 36. In line astern formation the correct fore and aft position can be judged by the relative size of the aircraft ahead, or a part of this aircraft as seen relative to the windscreen of the formating aircraft. The amount by which each aircraft must be stepped down from the preceding aircraft varies according to the slip-stream from each type of aircraft, but generally should be as small as possible. Too large a vertical interval between aircraft results in the last member of the formation flying very much lower than the leader and this may cause some difficulty in turns. 34.3.5-19
KEEPING STATION 37. All pilots aim to achieve smoothness in their formation flying. This is particularly important when more than a single aircraft is formatting in echelon, line astern or line abreast, since the movement of one aircraft in relation to another is accentuated towards the outside of the formation. If the second aircraft in the formation is flown roughly, the pilot of the aircraft on the outside of the formation will have an extremely difficult task. Sometimes, his only option is to keep station on the lead aircraft instead of the one in between, thereby reducing the whip effect. 38. To keep his position constant in relation to the leader of the formation, the formatting pilot may be required to adjust his position longitudinally, laterally and/or vertically. A keen sense of anticipation must be developed so that correcting movements are kept to a minimum. 39. Longitudinal Station Keeping. Changes of position in the longitudinal direction are made using the throttle to make small speed changes and this in turn may necessitate a small movement of the elevators to maintain position vertically; thus co-ordinated movements of the two controls are made throughout. To maintain a constant position longitudinally the throttle should be moved in the appropriate direction immediately any change is noticed or anticipated. This movement should be smooth and no more than is necessary to correct errors, large throttle movements will usually result in over-correction, making station keeping difficult and increasing fuel consumption; the latter may be critical on long sorties. It must be remembered that a clean aircraft usually accelerates quickly and decelerates slowly because of its low drag and due allowance must be made for this. Jet engine aircraft may have poor acceleration, especially at low air speeds, and also decelerate slowly; both effects must be anticipated. 40. Lateral Station Keeping. Changes in lateral position are made by gentle movements of aileron, in some aircraft, co-ordinated with use of rudder. Small angles of bank should be used to correct lateral spacing and, when approaching the correct position, opposite bank will be required to return to the leader s heading and so maintain the new position. 41. Vertical Station Keeping. Position in the vertical plane is controlled by the elevators. At some stages of flight, notably on an approach, in aircraft with highly swept wings, even small changes of angle of attack caused by elevator movement will require some throttle movement to maintain longitudinal positioning. Co-ordination of elevator and throttle is important. CONCLUSION 42. Clearly, formation flying has much to offer, and it is an integral part of every military pilot s inventory of skills. By now you should understand what is involved, and will more readily appreciate the performances of those whom you see at air shows and on your visits to RAF stations. 34.3.5-20